explorations now: Describe what you do for a living.AS: I’m interested in marine bioacoustics. I use sound to study marine animals and events that occur and produce sounds in the marine environment, anthropogenic or natural. In terms of marine animals, by using sound we can learn about their biology, distribution, abundance, habitat use. But also I’m interested in noise, the interactions of animals and anthropogenic sounds, and the effect of anthropogenic sounds on the animals.

en: How did you select this as a career?AS: I grew up in Croatia and I spent my summers on the coast of the Adriatic. I loved spending time by the water, swimming and snorkeling. I think I was about 12 or 13 when I realized the sea could be part of a career option, that I could be an oceanographer. And that was it, that’s what I really wanted to do. In Croatia, however, science is not the best career option so I started my undergrad studies in electrical engineering, because that would’ve been a wise career choice. After a couple of years, I had an opportunity to transfer and finish my studies in the U.S. Once here, I chose a degree in biology. That combination of engineering and biology turned out to be a perfect setup to do bioacoustics. When I was applying to grad schools it seemed that the researchers most interested in my background were people doing tech-y things. John Hildebrand, who is a professor here at Scripps, contacted me about a project to study marine mammals in the Antarctic using acoustics. That sounded very cool, and it blended well with my undergrad experiences. So I kind of fell into bioacoustics after a somewhat circuitous route, but I always knew I wanted to be an oceanographer. I always loved the ocean and learning more about it never ceases to fascinate me.

en: Why did you choose Scripps?AS: When I was looking for graduate school, the choice of Scripps was a no brainer. For an aspiring oceanographer, there's hardly a better place to go. And I thoroughly enjoyed all the opportunities students at Scripps have in front of them: oceanographic cruises, great people to talk to just down the hall or in a nearby building, student-only funding to travel to meetings and network. When you are here, however, it's easy to take for granted all those resources. Being away from Scripps for four or five years, I was reminded of how special Scripps is and I enjoy being back and having access to those resources again.

en: What are some of the major questions in your field?AS: There are a couple of different aspects I would say are currently big in our field. Acoustics give us a chance to listen to animals that are difficult to study otherwise so we’re just learning many basic, foundational things about different species, while still developing technology for answering biologically important questions. One of the big areas of focus recently has been how to use passive acoustics to study abundance of populations. It can be hard and very expensive to conduct extensive boat-based surveys, which is the more traditional way to estimate abundance. Passive acoustics offer potentially a more cost-effective way to do this.
The second area that is becoming more and more important is understanding the impacts of sounds on animals – marine mammals specifically – but also fish and other ocean animals. I think this is coming to the forefront as we realize the oceans are getting noisier, mostly because of increases in shipping. There’s a lot of impetus to try to understand how that increase in background noise affects animals that produce sound and count on sound for all kinds of biologically important things such as mating and finding food.

en: How long have scientists been studying sound in the ocean?AS: The field of acoustics or bioacoustics specifically dates to World War II, the '40s and '50s, when Naval sonar operators started noticing weird repetitive persistent sounds in their sonar displays. At the time, there were concerns those were Russian submarines, but it turned out they were baleen whales that make very loud stereotyped sounds that propagate over long distances. That started the field of marine bioacoustics in general. In terms of our understanding of what increasing noise in the ocean means for the animals, I would say that probably since the 1990s and especially in the 2000s, there have been an increasing number of studies addressing the issue. A seminal event occurred in 2000, when a group of beaked whales stranded in the Bahamas during a Naval exercise. Since then the Navy has been very interested in trying to understand the impact their sonar has on marine mammals. That has brought in a lot of funding and really helped us make substantial advances in the field.

en: What are some of the tools and methods that you use to do your research?AS: The basic tool that we use is an underwater acoustic recorder. At Scripps we have High Frequency Acoustic Recording Packages, developed in John Hildebrand’s lab and these have allowed us to collect large datasets. We now have 10-13 years of data from Southern California for example. In the whole process of data acquisition, we start with an instrument and deploy it somewhere in the world. Usually they’re deployed for a long time period – six months or up to a year – and when the data come back, they are processed and analyzed.
We’ve been developing different automatic detectors that run through the data and pick out specific signals that we are interested in. I’m mostly interested in baleen whale sounds. For example, we have a detector that allows us to pull out all the occurrences of blue whale calls or actually one particular type of blue whale call that’s common here off California. Then depending on specific questions you’re interested in, or have funding for, you can do additional processing or analyses. My day often consists of sitting at a computer and programming in [the science software program] Matlab.
It’s not particularly glamorous necessarily, but I think it’s really exciting because by looking at these years of data in different ways, you can learn new things and see patterns that probably nobody has seen before. I get to think about what they mean and how you would go about testing those hypotheses – it’s exciting, science-in-progress kind of work. In that way, what I do is a lot of observational science, which I think is an important part of science in general but tends to get overlooked in your textbook description of how science is done.

en: What are your current projects?AS: One of the projects I’m working on right now is funded by the Office of Naval Research. We are taking those years of data from the Southern California Bight that I mentioned and are pulling out all the blue and fin whale calls in the datasets. We have very good temporal resolution in these data. I can tell you how many blue whale calls were detected daily at each site and we’re trying to use that information in conjunction with various environmental data that are collected by remote sensing like sea surface temperature, sea-surface height, and chlorophyll concentration, to get a sense of habitat preferences for calling blue and fin whales. It’s really a basic research question, but it is of interest for the Navy. They need better prediction tools to plan their exercises in the region and develop impact statements. Even this basic research feeds into the applied, mitigation side of the spectrum.
Also I am collaborating with the (NOAA) Pacific Islands Fisheries Science Center; we’ve been looking at trends in ocean noise over the last several years in the western and central Pacific. Currently, we are describing different anthropogenic sources of noise at those locations. Many of the sites are in fairly remote areas - atolls and islands throughout the Pacific, but also some inhabited areas like Saipan. The noise there is mostly local boat noise and in the case of Hawaii, potentially some Navy training-related sounds as well. We’re interested in describing those anthropogenic noises but also looking at whether there are impacts on the humpback whale calling behavior from anthropogenic sources.

en: What evidence exists that human activities are directly influencing the behavior of marine animals?AS: There are a sizeable number of studies that have looked at various aspects of this and it’s not a straightforward answer. For example, there is a study going on right now off the coast of California looking at the behavioral response of cetaceans to Navy sonar. They just published several papers indicating that the response of blue whales to sound that is similar to sonar depends on the activity of the animals. When they’re feeding, it could be disruptive but at other times the response is less clear.
A recent study included results from opportunistic data collection. After 9/11, there was a period when there was less shipping than usual on the East Coast. The researchers happened to be collecting samples at the time that allowed them to measure stress-related hormones in right whales. They found a drop in stress hormones during the time period with reduced shipping. We don’t really understand how this works but we do know that background noise in the ocean has increased dramatically in the last 30 to 40 years and we know that the animals use sounds to find mates and food, so it’s not unreasonable to expect they would be experiencing stress as it becomes harder to accomplish those things.
Really intense sound can cause injuries, just like if you go to a rock concert your ears will hurt afterward. But more often, response and effects from noise are a lot more subtle. A really counterproductive reaction of some animals, when they’re trying to avoid disturbing sounds, is to come up from the deep to the surface. However, if the sound they’re trying to avoid is a ship, once they come to the surface, they become susceptible to ship strike. So getting out of the way of a sound that is disturbing doesn’t always put you in a safe place. Because there are a number of ways animals can deal with noise, it is hard to answer questions on overall impact.

en: What are some of the barriers scientists face to getting their research done?AS: When you talk to old salts, they seem to think that there aren’t the same opportunities available today as there used to be. And I tend to believe them because I feel that in general, young people today don’t have the opportunities that people coming out of college 40 years ago did. One of the things I notice is a lack of opportunity to do large projects, go out to sea, do expedition-type science. I don’t think funding agencies today are really interested in that. I am productive because a lot of what I do is using data that have been collected over the years. That’s a lot cheaper than going out to sea and collecting new data. I’d love to go to sea and collect more data but the proposals that I’ve written recently to do that sort of thing haven’t gotten funded.
I think that’s a sad development because some of my greatest learning experiences were at sea, seeing how to do oceanography. Being on a ship with physical and chemical oceanographers, they would do CTD casts and put up plots of what the hydrography looks like right now. Discussing the data there and then were fantastic learning moments. It was great to be a part of a large project in terms of my personal learning, but also there was a whole cohort of students who went on these cruises with me and we all learned together and formed friendships and collaborations in the process. I fear that may be getting lost among the current financial issues that seem to result in insufficient support for basic oceanography at sea.